I wanted to combine the GT10 effects with the spider valve amp sounds...

You could still run the GT-10 in stompbox mode and run it into the front of your SpiderValve. You might have to disengage the preamps in the GT-10 to get the best sound that way so you're not having dueling preamps.

The best would be probably just use a nice clean sound on your amp and then use the BOSS for all the other dist effects and what not.